This project proposes the development of a prosthetic wrist unit, which has powered rotation and flexion. Upper limb prosthetic devices are poorly accepted in the United States with rejection rates up to 50% [13]. There are nearly 2 million amputees in the United States. 26,000 upper limb amputations are performed per year, of which approximately 10-12,000 would be a candidate for this prosthetic device. Powered flexion is an important addition to an externally powered prosthesis. Flexion and extension, along with rotation give the prosthesis two additional degrees of freedom, which when added to the range of motion for the shoulder and elbow yield a six-degree of freedom system. Six-degrees of freedom, the goal of most robotic systems, allows placement of the hand throughout the entire workspace. Without flexion, amputees cannot reach a number of positions and must use compensatory motions for many other movements. This ability to flex the wrist is critical for bilateral patients and may be an important link to reducing the rejection rate of powered prosthesis. [unreadable] This work is based on a working plastic prototype, designed in Pro/ENGINEERZ and made via stereolithography, a layered manufacturing process. The wrist will be compatible with current myo-electric prosthetic hands. This unique design has two motors, one for rotation and one for flexion/extension, which enable the wrist to pronate/supinate 360:, to extend 30:, and to flex 60:. Movement is proportional to sensor signal level and will be controlled with EMG sensors, for which the target population will need two available EMG sites. This wrist will function for trans-radial, trans-humeral and shoulder disarticulation amputation levels. [unreadable] Following completion of clinical testing of the production prototype during phase two, this product will be marketed for licensing to the three major manufacturers of upper limb prosthetic componentry: Motion Control (Salt lake City, Utah), Liberating Technologies (Boston, MA), and Otto Bock (Duderstadt, Germany). These companies are most likely to have an interest in this product because it will complement their existing product line of upper limb powered prosthetic components. [unreadable] [unreadable]